The present invention relates to thermosettable resins such as epoxy resins, epoxy vinyl ester resins, unsaturated polyester resins, fiber-reinforced plastics (FRP), coatings and composites; and methods of producing these.
Epoxy resins, epoxy vinyl ester resins and unsaturated polyester resins are known for their thermal and chemical resistance. They also display good mechanical properties but they lack toughness and tend to be very brittle. This is especially true as their crosslink density or Tg increases.
Attempts have been made to strengthen or toughen epoxy resins, epoxy vinyl ester resins and unsaturated polyester resins by incorporating therein a variety of elastomeric materials. Examples of toughened epoxy resins are disclosed in U.S. Pat. Nos. 3,923,922; 4,221,697; 4,117,038; 3,856,883; 3,496,250; 4,082,895; 3,496,250; 3,316,195; 3,499,949 and 3,509,086; as well as European Patent Application No. 78,527, published Nov. 5, 1983: and Japanese Patent No. 55-018401.
A summary of epoxy and elastomeric blend technology is provided in Rubber-Modified Thermoset Resins, American Chemical Society (1984). Primarily, attempts to toughen epoxy compounds have focused on employing liquid rubbers, such as carboxyl-terminated butadiene-acrylonitrile copolymers. In certain amine cure systems, the rubber separates into distinct particles. However, the rubber must first be prereacted with the epoxy resin to ensure compatibility, and optimum cure properties, and such rubbers do not exhibit latent reactivity to the resins.
Prior technology required specific curing conditions to be followed in order to develop the right rubber particles morphology and obtain the toughening effect.
It would be desirable to provide a technology which would allow performance of the thermosettable resin blend to be independent from the curing schedule, therefore allowing a more robust coating.